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The Brain – The Central Core
The human brain is the product of millions of years of evolution.There are 3 layers that evolved in different stages of evolution : 1)The primitive central core 2)The limbic system which evolved later 3)The cerebral hemispheres which in charge of higher mental processes. At the point where the spinal cord enters the skull, it becomes the hindbrain. Hindbrain is found in even the most primitive vertebrates, it is believed that the earliest part of the brain to evolve. Hindbrain (central core) is the area containing the : medulla,pons, and cerebellum.
Medulla
Controls essential life support functions including respiration, heart rate, and blood pressure.
Pons
Maintains the sleepwake cycle
Cerebellum
Controls certain reflexes and Coordinates body’s movements.
Midbrain
Hearing, sight and pain registration.
Thalamus
Over the brainstem 2 egg shaped structures. Relay station: All sensory information from sensory receptors to the brain passess through, except those for smell.
Hypothalamus
Motivation (hunger, thirst, sexual drive, body temperature) and emotion(rage, terror, and pleasure). Stress reaction.
Reticular formation
Network of neurons found throughout the brain. Job is to send ‘Alert!’ signals to the higher parts of the brain. During sleep RF is turned down. Permanent damage to the RF can induce coma. Anesthesics work by temporarily shutting down the system off. Ring of structures located between the central core and the cerebral hemispheres. Important to learning and emotional behavior. It is more recent than central core and fully developed in only mammals(Fish and reptiles have primitive lymbic systems and their patterns of feeding, attacking and mating are fixed). Parts of the lymbic systems: Hippocampus essential in formation of new memories. When damage to the area, people still remember names, faces, and event before injury but can’t remember anything new. Amygdala is important for regulating emotions. Self perservation emotions(Agression, fear and panick, and pleasure) Also ability to read facial expressions of emotion in other people are registered in limbic system.
Cortical function
Prosopagnosia/Right temporal area/Fusiform face recognition area (FYA)
The limbic system
Electrode implanted in reward center. ( bu kısımların adı geçiyor anlaşılmadı)
The Cerebral Cortex
Brain is divided into right and left hemispheres Each hemisphere can be divided into 4 lobes by crevices. It is the most recently evolved part of the brain. Fish have no cortex, reptiles and birds have only primitive cortex
Primary somatosensory cortex and Primary motor cortex : Phineas Gage case, thick iron damaged frontal lobe. Personality change(Loss of motivation, and concentration). Ability to make judgments goal directed behavior, emotional control are impaired.
Hemispheric Specialization
Corpus Callosum : Fibers that connect the two hemispheres. Allows close communication between left and right hemisphere.
Each hemisphere appears to specialize in certain functions.
Split Brain
It is a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them. Split-Brain Research Much information about functions of each hemisphere has come from studying split brain patients.
LANGUAGE
Human language is controlled primarily by the left cerebral hemisphere. Aphasias are impairments of the language. Broca’s aphasia : Tends to be expressive language problems(talking) Wernicke’s aphasia : Tends to be receptive language problems(listening).
Family of techniques that can image activity in the brain as it responds to various stimuli. EEG imaging : Measures brain activity on a milisecond by milisecond basis. Magentoencephalography (MEG) and Magnetic source imaging (MSI) : Similar to EEG but have greater accuracy Positron emission tomography(PET), Radioactive PET, Single photon emission computed tomography (SPECT) : Uses radioactive glucose to determine location of greatest brain activity. Functional magnetic resonance imaging (fMRI) : Measures movement of blood molecules within the brain. Functional MRI scan shows the visual cortex activated as the subject looks at faces.
The Spinal Cord
Complex cable of nerves that connects brain to rest of the body. Carries sensory (Afferent)information from extremities and internal organs to the brain. Carries motor(Efferent) impulses from the brain to internal organs and muscles. The spinal cord controls some protective reflex movements without any input from the brain.
The Somatic Nervous System
It is composed of : Afferent neurons(sensory) : Neurons that carry messages from sense organs to spinal cord. Efferent neurons(motor) : Neurons that carry messages from the spinal cord or brain to muscles and glands.
The Autonomic Nervous System
Carries messages between the central nervous system and the internal organs. Sympathetic division : Fight-or-flight response. Increases heart rate and breathing. Stops digestion. It tells endocrine system to start pumping chemicals into the bloodstream to strenghten these reactions. Parasympathetic division : Calms and relaxes body. Produces effects opposite to those of the sympathetic division. Reduces heart rate and breathing. Restores digestion .( Pupils contract: göz ile alakalı galiba ).
The Endocrine System
Helps coordinate and integrate complex psychological reactions. Radical change can cause psychological disorders exa: depression. Exa: During puberty they trigger development of secondary sex characteristics(breasts in females, deeper voive of males, pubic hair in both sexes). Endocrine glands are tissues that produce and release hormones. Hormones have the similar function with neurotransmitters: They carry messages.
Adrenal glands : Located above the kidneys. Secretes hormones in reaction to stress. Epinephrine activate the sympathetic NS, and norepinephrine prolongs the response to stress.
Genes, Evolution, and Behavior
Genetics : Genetics is the study of transmission of a trait from one generation to next. Chromosomes : Pairs of thread like bodies that contain genes. Human beings have 23 pairs of chromozomes in every normal cell. Deoxyribonucleic acid (DNA) : Main ingredient of chromosomes and genes. Contains the “code of life”. Genes are elements found on chromosomes that control the transmission of traits. Human genome is the full complement of the genes and chromosomes of an organism. Dominant genes are member of a gene pair that controls the appearance of a certain trait. Recessive genes are member of a gene pair that can control the appearance of a certain trait only if it is paired with another recessive gene. Polygenic inheritance is a process by which several genes interact to produce a certain trait; responsible for our most important traits.
Behavior Genetics
Study of behavior from a genetic perspective. Animal behavior genetic studies include: Strain studies : Studies of the heritability of behavioral traits using animals that have been inbred to produce strains that are genetically similar to one another. When animals from different strains are raised together in the same environment, differences between them largely reflect genetic differences in the strains. Selection studies : Studies that estimate the heritability of a trait by breeding animals with other animals that have the same trait. Guard dogs need to be agressive and loyal, herding dogs need to be control large number of animals etc.
Human Behavior Genetics
Family studies : Assume that close family members share more of a trait than non-relatives. Used to assess the heritability of psychological disorders or traits. Twin studies : Used to determine how heritable a trait or disorder may be. Identical twins would have highest heritability. identical twins are twins developed from a single fertilized ovum and therefore identical in genetic makeup at the time of conception. fraternal twins
are twins developed from two separate fertilized ova and therefore different in genetic makeup. Adoption studies : Used to assess the influence of environment. Molecular genetics : Direct study of the genetic code.
Evolutionary Psychology
Natural selection : “Survival of the fittest”, those organisms that are best adapted to their environments are most likely to survive and reproduce.
Evolutionary psychology looks at the adaptive or survival value of behaviors (not the
structural changes in organisms as evolutionary biologists do). Our brains are prewired to learn some things more easily than others, to analyze problems in certain ways, and to communicate in distinctively human ways. Ex. Learning language. All children acquire language from different cultures about at the same age and predictable stages and the underlying structure of all human languages is basically the same (noun and verbs, subjects and objects, questions and conditional phrases). Social Implications New challenges have arisen as a result of our better understanding of genes. Study of biological origins of behavior could lead to genocide and eugenics aimed at eliminating certain types of people Could also be used to create new categories of people, such as people bred to be good soldiers or manual laborers.
